Fiber reinforced composite liner for lining an existing conduit and method of manufacture

ABSTRACT

A reinforced liner for cured in place pipe rehabilitation of an existing pipeline having a plurality of high-strength low-elongation fiber bundles disposed circumferentially around the tubular liner at both inner and outer surfaces of a resin absorbent layer of the liner is provided. The bundles of reinforcing fibers are continuous lengths of high modulus fibers laid circumferentially with the ability to stretch to accommodate variations in host pipe diameter. The fibers on the inner surface are secured to a porous scrim to form an inner tubular reinforcing layer. A resin absorbent layer is formed into a tube about the inner layer. An outer layer of bundles of reinforcing fiber are formed into a tube about the absorbent layer. An outer impermeable tubular layer is wrapped around the inner layers. The reinforcing layer may include longitudinal reinforcing fiber in either or both reinforcing layers to increase the longitudinal strength of the liner.

This application is a continuation of Ser. No. 10/098,972 filed on Mar.14, 2002 now U.S. Pat No. 6,708,729.

BACKGROUND OF THE INVENTION

This invention relates to a fiber reinforced composite liner of flexibleresin absorbent material, and more particularly to a composite linerhaving bundles of high-strength low-elongation fiber layers disposedcircumferentially around the tubular liner adjacent to both inner andouter surfaces of the liner with at least one layer of resin absorbentmaterial between the fiber reinforcing layers to increase the resistanceto buckling of the cured liner.

It is generally well known that conduits or pipelines, particularlyunderground pipes, such as sanitary sewer pipes, storm sewer pipes,water lines and gas lines that are employed for conducting fluidsfrequently require repair due to fluid leakage. The leakage may beinward from the environment into the interior or conducting portion ofthe pipelines. Alternatively, the leakage may be outward from theconducting portion of the pipeline into the surrounding environment. Ineither case, it is desirable to avoid this leakage.

The leakage may be due to improper installation of the original pipe, ordeterioration of the pipe itself due to normal aging or to the effectsof conveying corrosive or abrasive material. Cracks at or near pipejoints may be due to environmental conditions such as earthquakes or themovement of large vehicles on the overhead surface or similar natural orman made vibrations, or other such causes. Regardless of the cause, suchleakages are undesirable and may result in waste of the fluid beingconveyed within the pipeline, or result in damage to the surroundingenvironment and possible creation of a dangerous public health hazard.If the leakage continues it can lead to structural failure of theexisting conduit due to loss of soil and side support of the conduit.

Because of ever increasing labor and machinery costs, it is increasinglymore difficult and less economical to repair underground pipes orportions that may be leaking by digging up and replacing the pipes. As aresult, various methods had been devised for the in place repair orrehabilitation of existing pipelines. These new methods avoid theexpense and hazard associated with digging up and replacing the pipes orpipe sections, as well as the significant inconvenience to the public.One of the most successful pipeline repair or trenchless rehabilitationprocesses that is currently in wide use is called the Insituform®Process. The Insituform Process for the cured in place pipe (“CIPP”)installation is described in U.S. Pat. Nos. 4,009,063, 4,064,211 and4,135,958, the contents of all of which are incorporated herein byreference.

Flexible tubular liners suitable for use in the Insituform Process aregenerally flexible tubes of two or more layers of resin absorbentmaterial. Typically the resin absorbent material is a needled felt of asynthetic fiber, such as polyester, but may be acrylic, polypropylene,or an inorganic fiber, such as glass or carbon. The cured-in-place-pipeliner generally includes two or more layers of resin absorbent material,but may include several layers, depending on the desired ultimatethickness of the liner and the diameter of the conduit to be lined. Theinner tubular layer or layers are usually uncoated on both sides. Theouter layer has an impermeable layer on the outer surface so that resinimpregnated into the resin absorbent layers may be retained within theresin absorbent material. A method for producing such flexible tubularliners having at least two layers with the outer layer having an outerimpermeable layer is described in detail in U.S. Pat. No. 5,285,741. Thecontents of this patent are incorporated herein by reference.

There are many suggestions in the prior art to reinforce a CIPP liner byaddition of filamentary or other materials. The '063 Patent suggestsattaching a scrim web to the filled layers. Similarly, in WO 91/14896 Isuggest wrapping one or more reinforcement layers of a synthetic fiberand/or glass about an inner resin absorbent tube to increase the hoopstrength of the resulting rigid pipe. An outer resin absorbent tubehaving an impermeable coating is disposed about the reinforcement layeror layers. It had been earlier suggested by Eric Wood in U.S. Pat. No.4,836,715 to incorporate reinforcing layers near the inner and outersurfaces of the lining to simultaneously protect against buckling andovality, respectively. The reinforcing fabric layers are provided in theform of fabric layers of glass and polyamide that extend generallycircumferentially of the tubular lining. More recently, in U.S. Pat. No.5,868,169 a layer of reinforcing fibers, such as fiberglass isencapsulated between layers of resin absorbent material saturated withresin. The reinforcing fibers in the form of a mesh or mat of fiberglassare fixedly attached to the inner and outer layers of resin absorbentmaterial.

In the standard practice of the Insituform Process an elongated flexibletubular liner of a felt fabric, foam or similar resin absorbent materialwith an outer impermeable coating is impregnated with a thermosettingcurable resin. Generally, the liner is installed within the existingconduit utilizing an eversion process, as described in the later twoidentified Insituform patents. In the eversion process, radial pressureapplied to the interior of an everted liner presses it against and intoengagement with the inner surface of the pipeline. The InsituformProcess is also practiced by pulling a resin impregnated liner into theconduit by a rope or cable and using a separate fluid impermeableinflation bladder or tube that is everted within the liner to cause theliner to cure against the inner wall of the existing pipeline.

A curable thermosetting resin is impregnated into the resin absorbentlayers of a liner by a process referred to as “wet out.” The wet-outprocess generally involves injecting resin into resin absorbent layersthrough an end or an opening formed in the outer impermeable film,drawing a vacuum and passing the impregnated liner through nip rollersas is well known in the lining art. One such procedure of this vacuumimpregnation is described in Insituform U.S. Pat. No. 4,366,012, thecontents of which are incorporated herein by reference. A wide varietyof resins may be used, such as polyester, vinyl esters, epoxy resins andthe like, which may be modified as desired. It is preferable to utilizea resin which is relatively stable at room temperature, but which curesreadily when heated with air, steam or hot water, or subjected toappropriate radiation, such as ultra-violet light.

The CIPP flexible tubular liners have an outer smooth layer ofrelatively flexible, substantially impermeable polymer in its initialstate. When everted, this impermeable layer ends up on the inside of theliner after the liner is everted during installation. As the flexibleliner is installed in place within the pipeline, the liner ispressurized from within, preferably utilizing an eversion fluid, such aswater, air, or steam to force the liner radially outwardly to engage andconform to the interior surface of the existing pipeline. Typically,cure is initiated by introduction of hot water into the everted linerthrough a recirculation hose attached to the end of the everting lineror by introduction of steam. The resin impregnated into the absorbentmaterial is then cured to form a hard, tight fitting rigid pipe liningwithin the existing pipeline. The new liner effectively seals any cracksand repairs any pipe section or pipe joint deterioration in order toprevent further leakage either into or out of the existing pipeline. Thecured resin also serves to strengthen the existing pipeline wall so asto provide added structural support for the surrounding environment.

While the present suggestions to increase strength and resistance tobuckling of the cured liner are available, use of high modulus fiberlayers substantially increase the cost of raw materials and introducedifficulties in handling webs and attaching them to one of the resinabsorbent layers. Moreover, it has been found that placement of layersof reinforcing fiber between layers of resin absorbent material does notprovide for sufficient increases in buckling resistance to justify theadditional costs. Thus, the prior art does not teach a construction thatallows obtaining the desired improvements by placing reinforcing fibersat the outside surfaces of the composite.

Accordingly, it is desirable to provide a reinforced liner that canprovide increased resistance to buckling at a reduction in cost comparedto liner presently utilized and disclosed in the prior art.

SUMMARY OF THE INVENTION

Generally speaking, in accordance with the invention, a reinforcedcomposite tubular liner for cured in place pipe rehabilitation of anexisting pipeline having a plurality of high-strength low-elongationfiber bundles disposed circumferentially at the inner and outer surfacesof the liner is provided. The bundles of reinforcing fibers arecontinuous lengths of reinforcing fibers laid out in tubular formadjacent to and parallel to each other on the inner and outer surfacesof at least one resin absorbent tubular layer therebetween. The innerreinforcing layer is bundles of reinforcing fibers that may be attachedto a thin porous scrim folded over and stitched along the edge to form atube. A resin absorbent layer or layers are wrapped about the innerreinforcing tubular layer and joined at the edges to form a tube. Theresin absorbent layers are formed into tubes by any convenient means,such as sewing, flame bonding, or adhesively joined. An outerreinforcing layer of reinforcing fiber bundles held together bylongitudinal stitching is then wrapped around the resin absorbent layerto form an outer tubular layer with the ends of the bundles ofreinforcing fibers overlapping. This allows the reinforcing fiberbundles to slide past each other when the tube is everted and expanded.

The increase in stiffness of the cured liner allows for a reduction ofthickness of the resin absorbent layer and corresponding reduction inamount of resin used. This offsets any increase in cost due to the highmodulus fiber and manufacturing costs. It is possible to reduce theweight of resin by half and yet obtain buckling strengths 50 percentmore than for a non-reinforced liner. The reinforcing fiber bundles arelaid out so that they are present between about 1 bundle every inch toabout 3 or 4 bundles per inch. The reinforcing fibers can be anyhigh-strength low-elongation organic fiber, such as polyester,polypropylene, nylon, carbon, Aramid, or inorganic fiber, such as glassor steel. In the preferred embodiment, the reinforcing fiber is carbonfiber.

Accordingly, it is an object of the invention to provide an improvedreinforced cured in place liner that provides increased resistanceagainst buckling with less resin than presently available.

It is another object of the invention to provide an improved reinforcedcured in place liner having at least two reinforcing layers on theoutside surfaces of at least one resin absorbent layer at the surfacesof the liner.

Yet another object of the invention is to provide an improved reinforcedcured in place liner having increased stiffness to increase bucklingresistance.

Still another object of the invention is to provide an improvedreinforced cured in place liner having lower overall material cost andmanufacturing cost.

A further object of the invention is to provide an improved fiberreinforced cured in place liner having reduced thermal shrinkage aftercuring,

Still a further object of the invention is to provide an improvedreinforced cured in place liner of reduced thickness and weight toprovide reduced resistance to flow.

Yet a further object of the invention is to provide an improvedreinforced composite cured in place liner so that extremely long lengthsof liner can be pulled into an existing conduit prior to inflation.

It is another object of the invention to provide an improved method ofmanufacture of a fiber reinforced cured in place liner.

Still other objects and advantages of the invention will in part beobvious and will in part be apparent from the specification.

The invention accordingly comprises the several steps and the relationof one or more of such steps with respect to each of the others, and theproduct which possesses the characteristics, properties and relation ofconstituents, all as exemplified in the detailed disclosure hereinafterset forth, and the scope of the invention will be indicated in theclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a composite reinforced cured inplace liner constructed and arranged in accordance with the invention;

FIG. 2 is a cross-section of the liner of FIG. 1 taken along line 2—2;

FIG. 3 is a plan view showing bundles of reinforcing fibers stitched toa porous netting material;

FIG. 4 is a schematic perspective view of the stitched reinforcingfibers of FIG. 3 formed into a tube;

FIG. 5 is a cross-sectional schematic view showing the seam of the tubeof FIG. 4 folded back for expansion;

FIG. 6 is a cross-sectional in schematic view of an alternativearrangement for folding the inner reinforcing layer of FIG. 4;

FIG. 7 is a cross-sectional schematic view illustrating wrapping of aresin absorbent layer about the inner reinforcing layer of FIG. 5;

FIG. 8 is a plan view of the reinforcing layer of stitched carbon fiberto be wrapped around the resin absorbent layer of FIG. 7;

FIG. 9 is a cross-sectional schematic view illustrating the outerreinforcing layer wrapped about the resin absorbent layer of FIG. 7;

FIG. 10 is a perspective view showing another composite reinforced curedin place liner constructed and arranged in accordance with theinvention;

FIG. 11 is a schematic cross-section view showing an arrangement ofelements of the liner of FIG. 10; and

FIG. 12 is a schematic sectional view illustrating a typical eversion ofa cured in place pipe liner.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

By incorporating high modulus fibers in the lining structure theflexural and compressive moduli of the lining can be increased so thatthinner linings can be used for a given design pressure. Suchreinforcing fibers may be arranged in one axis, in one plane or randomlyin all three axes (as with standard felt), but the volume fraction ofthe reinforcement is minimized and the axial modulus and strength aremaximum when the fibers are in one axis and reduce rapidly when theother structures are used. Linings require circumferential strength andstiffness so fibers should be aligned in the circumferential directionand the most economical use is in two layers at the outside surfaces.

The following table compares properties of glass fibers and certainavailable lower cost carbon fibers.

TABLE I Uni-directional Uni-directional Bi-axial Property Carbon FiberGlass Fiber Carbon + resin Glass + resin Glass + resin Tensile 450,000350,000 182,000 161,000 80,000 Strength psi Tensile 33,000,00011,600,000 21,000,000 7,500,000 3,000,000 Modulus S.G. 1.7 2.54 1.5-1.62-2.1 Elongation 1.2 4.6 1.2 3.5 ? At break Flexural 290,000 170,00080,000 Strength Flexural 18,000,000 7,500,000 2,800,000 Modulus

The optimum design uses the reinforcing fibers near the outside of thelaminate with the (relatively) low cost per unit volume resin/felt atthe center.

Theory predicts that the flexural modulus of the composite will be givenby the expression:E _(F) =E _(resin)+(E _(reinf) −E _(resin))×(t ₂ ³ −t ₃ ³)/t ₁ ³

The compressive modulus is:E _(comp) =E _(resin)+(E _(reinf) −E _(resin))×(t ₂ −t ₃)/t ₁

Where t₁=overall thickness and t₂ and t₃ are the thicknesses at theoutside and inside of the reinforcement respectively. E_(resin) is themodulus of the resin and felt matrix and E_(reinf) is the modulus of thereinforcement plus resin.

The inclusion of relatively high cost per unit volume reinforcing fibersin any direction other than the hoop direction will increase the costper unit volume without increasing the moduli in the hoop direction northe ability to withstand external pressure. Even includingcircumferentially oriented fibers near the center of the composite onlyincreases cost without increasing the flexural modulus although theywill increase the compressive modulus.

The theory above shows how fibers with moduli significantly higher thanthe resin/felt can be used to achieve high laminate moduli. Typicalfibers include glass, carbon, Aramid and the like. Any fiber with a highmodulus and the ability to adhesively bond to the resin may be used andthe fiber used will be chosen on the basis of the economics andenvironmental factors so that it will not degrade in service.

Conveniently the fibers are made into the weft (cross direction) threadsof a fabric structure. This may be done by a weaving process but in thepreferred embodiment they are sewn onto a previously made fabric orfelt. It is necessary, for wetting out the linings with resin, that thefabrics will allow the passage of resin through themselves. In apreferred embodiment of the invention one fabric (as shown in FIG. 3) aknitted net layer made of polyester, nylon or other suitable fiber, withthe reinforcing fibers sewn across it. Another fabric may be a thin feltlayer of similar fibers, again with the reinforcing fibers sewn across.The thin felt may be produced by any of number of means including needlepunching, spun bond, hydro-entangled and thermal bond. Another usefulfabric is shown in FIG. 8 in which the reinforcing fibers are held onlyby the longitudinal stitching. The weight of fiber per unit area offabric may be varied by using differing weights of fiber per unit lengthor by varying the spacing between the fiber bundles. The weight per unitarea can thus be controlled to give the desired properties as explainedin the theory above.

In one embodiment of the invention one or both layers of fabricincorporate longitudinal reinforcing fibers to control longitudinalstretch. These fibers are sewn into the fabric by the same threads thatsecure the circumferential fibers.

Typically the reinforcing fibers are sewn to the backing fabrics withlongitudinal chain stitches spaced at intervals ranging from about threeper inch to about one per two inches across the width. The advantage ofsewing the reinforcing fibers to fabric materials is that the edges ofthe fabric materials may be joined by sewing or other means to formtubular structure with circumferential reinforcing fibers. However, inone embodiment of the invention tubular structures are made by circularweaving in which the reinforcing fibers are the circular weft and theyare woven or sewn to warp threads of any suitable fiber such as nylon,polyester or other material.

In practice, pipes that need repair frequently vary in circumferenceover their length either because of inaccuracy during construction or bysubsequent wear and erosion. The tubes with which they are lined must beable to accommodate this variation in circumference and this is achievedby making them under size but with the ability to stretch up to themaximum circumference under the influence of the pressure of theinstallation fluid. Whereas the felt materials have good elongationcharacteristics the reinforcing fibers are substantially inextensible.In this invention the problem is overcome by providing substantialoverlaps in the reinforcing fibers which overlaps are free to slide toaccommodate the variations in circumference.

FIG. 1 illustrates in perspective a composite cured in place resinabsorbent liner 11 constructed and arranged in accordance with theinvention. Liner 11 is constructed from an inner reinforcing layer 12formed from a plurality of bundles of carbon fibers 13 on a porous scrimor netting layer 14. Carbon fibers 13 are secured in position spacedapart and parallel on netting 14 by a series of parallel stitches 15.Inner reinforcing layer 12 is formed by laying down a plurality ofbundles of carbon fibers in a predetermined pitch and securing in placeby a plurality of stitch lines 15. Inner reinforcing layer 12 is formedinto a tube by folding over and secured for handling by a longitudinalstitch line 16 along the folded edge.

A first inner resin absorbent layer 17 is wrapped about innerreinforcing layer 12 and formed into a tube by a butt seam 18. In theembodiment illustrated, resin absorbent layer 17 is a needled polyesterfelt, but may be any resin absorbent material, such as an acrylic or thelike. An outer resin absorbent layer 19 of the same resin absorbentmaterial is disposed about inner layer 17 and stitched along a seam 21for forming an outer resin absorbent tube.

An outer reinforcing layer 22 formed of a plurality of spaced bundles ofcarbon fibers 23 is disposed about outer resin absorbent layer 19. Outerreinforcing layer 22 include carbon fibers 23 stitched together by aplurality of stitches 24. Alternatively, carbon fibers 23 may bestitched to an open highly porous scrim, but in this embodiment aremerely stitched by stitches 24.

Finally, an outer impermeable layer 26 is disposed about outerreinforcing layer 22. Outer impermeable 26 is generally a thermoplasticfilm, such as polyethylene, polypropylene, polyurethane, PVC and thelike which will allow liner 11 to be inverted by fluids such as water,air and or steam. Outer layer 26 is secured into a tubular form by abutt seam 28 or other joining operations and overlaid with a tape 29 orextrusion for rendering outer layer 26 impermeable to fluids underpressure.

As shown in FIG. 3, inner reinforcing layer 12 is highly porous. Thispermits resin that will be impregnated into liner 11 to flow from onesurface to the other surface when liner 11 is in a lay flat conditionduring the typical wet-out procedure. This wet out procedure is wellknown in the art and one such process is described in U.S. Pat. No.4,366,012.

Reinforcing fibers 13 and 23 can be any high-strength low-elongationorganic or inorganic fiber. The modulus of a typical resin/polyesterfelt is between about 250 to 400×10³ p.s.i. Carbon fiber has a modulusof 33×10⁶ p.s.i. and glass is 10×10⁶. The physical properties of carbonfiber and E-glass compared to conventional resin/polyester feltmaterials are as set forth in Table II.

TABLE II E Modulus Relative Coefficient of Material p.s.i. DensityThermal Expansion* Resin/felt 250 to 400 × 10³ 1.2 to 1.3   30 × 10⁻⁶in/in ° F. Carbon Fiber 33 × 10⁶ 1.77 −.05 × 10⁻⁶ in/in ° F. E-Glass 10× 10⁶ 2.54 *Measured between 75° and 195° F.

Carbon fiber is known to be more expensive than glass for the samereinforcing property. However, as the price decreases this differencedisappears in view of the three times greater modulus of the carbonfiber compared to glass. This is due to the fact that the volume ofreinforcing fiber needed is inversely proportional to the modulus. Inview of this, only one-third the volume of carbon compared to that ofglass is required.

Examples of reinforcing fibers include glass, polyester, polypropylene,nylon, carbon, Aramid, steel and the like. Preferably the fiber iscarbon or glass. Fibers are available in bundles or tows containingmultiple single fibers. The tows may be combined to give the optimumamount of fiber reinforcement. In a preferred embodiment the tows are ofcarbon fiber and each tow contains between 30,000 and 100,000 individualfibers. Such tows will give between 200 and 750 feet per pound. Thespacing between the tows in the reinforcing layers may also be varied togive the optimum properties to the cured pipe liner.

If glass is used it may be type E glass bundles with strands having acontinuous length at approximately 750 feet per pound or about 2,000TEX. Each bundle of glass fiber has a break strength of about 250pounds. The weight of the glass bundles used may vary from about 100 to1,000 feet per pound, and preferably from about 350 to 900 feet perpound, and most preferably from about 500 to 800 feet per pound.

Carbon fiber reinforced composites are preferred because the carbonfibers are not subject to wicking and corrosion attack from acids andalkalis as are glass reinforced composites. This is an importantconsideration at lateral openings and at ends of the liners where thefiber in the composite may be exposed to effluent. This also allowsplacing the reinforcing carbon fibers at the surfaces of the compositewhere they are most effective in increasing stiffness. This increase instiffness is extremely sensitive to the thickness of any protectivelayers outside the reinforcing layers.

Depending on the amount of reinforcing fiber to be introduced, thepitch, or the space between repeating bundles can vary. For a typicalunderground gravity fed sewer main line, buckling strengths in excess of50% greater than available without the reinforcement can be obtainedwith a pitch varying from about 2 bundles per inch to about 4 bundlesper inch. Additional strength is obtainable by introduction ofadditional reinforcing fibers, but this benefit is offset by theadditional cost associated with addition of high performance materialsinto the CIPP liner.

The resin absorbent material of resin absorbent layers 17 and 19 may beof a wide variety of resin absorbent materials. This includes syntheticthermoplastic fibers such as polyester, acrylic, polypropylene, orinorganic fibers such as glass and carbon. Alternatively, the resinabsorbent material may be a foam. Typically, resin absorbent material 17and 19 is a felt of a polyester fiber, usually a needled felt as is wellknown in the CIPP art. Resin absorbent material 17 and 19 is formed intoa tube by a butt seam 18 and 21, respectively as is well known in theart and is described in U.S. Pat. No. 5,285,741. The tube can be joinedby any form of sewing, adhesive bonding or flame bonding.

Netting layer 14 is a highly porous sheet of organic or inorganicmaterials. It may be a thermoplastic material, such as a polyester,polyethylene or polypropylene film that is woven or non-woven orspunbond, or in the case of an inorganic material it may be a glass mat.In the embodiment illustrated herein, netting 14 is a polyester sheetsufficiently porous so that resin impregnated during wet-out will fullysaturate both sides of flattened liner 11.

As shown in FIG. 4, once carbon fibers 13 are secured to scrim 14 bystitches 15, reinforcing layer 12 is folded over itself with carbonfibers 13 to the outside. A stitch line 16 between both layers ofnetting 14 is made. This allows the stitched edges of reinforcing layer12 to form a fold 20 as illustrated in FIG. 5 or 6. This folding allowsfor inner reinforcing layer 12 to expand as liner 11 is everted duringinstallation and accommodate to variations in the host pipe diameter.Since inner reinforcing layer 12 will become the outer layer afterinversion, provision for this expansion must be built into compositeliner 11. In the embodiment illustrated, folding over stitched edge 16at fold 20 as shown in FIG. 5 or 6 allows for bundles of carbon fiber 13to slide past one another yet remain in the fixed orientation to providethe significant increase in buckling strength obtained in accordancewith the invention.

A cross-section of the composite including the inner reinforcing layerand first felt layer 17 is shown in FIG. 7. Outer reinforcing layer 22formed of parallel bundles of carbon fibers 23 is then disposed aboutthe outer most resin absorbent layer. Here, the edges of outerreinforcing layer 22 merely overlap each other so that bundles of carbonfibers 23 can slide past one another once liner 11 is everted andexpanded. This form of the liner at this point in assembly isillustrated in cross-section in FIG. 9.

Finally, an outer impermeable layer is wrapped about outer reinforcinglayer 22 to complete assembly of liner 11. Outer reinforcing layer 22 ofstitched carbon fibers illustrated in plain view and in FIG. 8. Outerimpermeable layer 26 is joined along a joint line 28 and a tape orextrusion 29 is applied to render outer impermeable layer impermeable tofluid under pressure. Outer impermeable layer may be any flexiblethermoplastic material which will render completed liner 11 impermeableto fluids. Such materials include polyurethane, polyethylene,polypropylene, PVC and the like.

Outer impermeable layer 26 includes a thin coating of resin absorbentmaterial 27 on the inner surface. Typically, this may be a fibrousmaterial identical to that of resin absorbent materials of resinabsorbent layers 17 and 19. Typically, between 1 to 2 mm in thickness isutilized. Absorbent material 27 allows for impermeable layer 26 to befirmly bonded to the rest of the composite. This also permits carbonfibers 23 to be as close to the inner surface of inverted liner 11 aspossible.

Inner reinforcing layer 12 and outer reinforcing layer 22 includingcarbon fibers 13 and 23 are stitched utilizing any convenient thread.Typically, this can be any polyester or cotton material as the resinsutilized are not corrosive and stitches are utilized to hold thepositions of the bundles of carbon fibers so that maximum resistance tobuckling is obtained in the final cured liner after installation.

Liner 11 may be installed in an existing conduit or pipeline by theeversion method as discussed below in connection with FIG. 12, or by thepull in and inflate method discussed above. In the case of pull in andinflate, a separate eversion bladder may be used to inflate the liner.However, it is possible to assemble a composite liner in accordance withthe invention having an integral inner bladder so that such a liner maysimply be pulled in and inflated with a fluid, that may be the curingfluid.

Referring now to FIG. 10, a composite cured in place resin absorbentliner 51 having an integral inner tubular impermeable bladder 52constructed and arranged in accordance with the invention is shown in anexisting conduit 50 in perspective. FIG. 11 shows liner 50 incross-section. Bladder 52 is of any flexible film material of the typethat may be used for impermeable layer 26 of liner 11. As in the case oflayer 26, bladder 52 may have resin absorbent material bonded to theinner surface facing the composite so that bladder 52 will bond securelyto the composite after cure.

Liner 51 is constructed by wrapping an inner reinforcing layer 53 of aplurality of bundles of carbon fibers 54 circumferentially about tubularbladder 51. Inner reinforcing layer 53 is formed by laying down aplurality of bundles of carbon fibers in a predetermined pitch andsecuring them in place by a plurality of longitudinal stitch lines 56.This may be formed in the same manner as outer layer 22 in liner 11.Inner reinforcing layer 53 is folded over bladder 52 with a generousoverlap. The overlap here and in any of the described reinforcing layersshould be between one and five inches, but preferably at least about twoinches in order to maintain the full strength of the structure.

A first inner resin absorbent layer 57 is wrapped about innerreinforcing layer 53 and formed into a tube by a butt seam 58 or anysuitable joining method, such as an overlap seam or adhesively bonded.In the embodiment illustrated, resin absorbent layer 57 is a needledpolyester felt, but may be any resin absorbent material, such as anacrylic or the like. An outer resin absorbent layer 59 of the same ordifferent resin absorbent material is disposed about inner layer 57 andstitched along a seam 61 for forming an outer resin absorbent tube.

An outer reinforcing layer 62 formed of a plurality of spaced bundles ofcarbon fibers 63 is disposed about outer resin absorbent layer 59. Outerreinforcing layer 62 include fibers 63 stitched together by a pluralityof longitudinal stitches 64. Alternatively, carbon fibers 63 may bestitched to an open highly porous netting as used in layer 12 of liner11, but in this embodiment fibers 63 are merely stitched by stitches 64.After wrapping about resin absorbent layer 59, layer 62 is stitched atthe edge by a longitudinal seam 66.

Finally, an outer impermeable layer 67 is disposed about outerreinforcing layer 62. Outer impermeable layer 67 is generally athermoplastic film as described above in connection with impermeablelayer 26 of liner 11. As in the case of layer 26, bladder 52 may haveresin absorbent material bonded to the inner surface facing thecomposite so that bladder 52 will bond securely to the composite aftercure. Outer layer 67 is secured into a tubular form by a butt seam orother joining operation and overlaid with a tape 69 or extrusion forrendering outer layer 67 impermeable to fluids under pressure. This willallow liner 51 to be everted if desired.

Liner 51 is designed for pulling into place and being directly inflated.For this method liner 57 is built in the opposite order from thatdescribed above with respect to liner 11. Outer reinforcing layer 62 inwhich reinforcing fibers 63 are sewn together as in FIG. 8 to a nettingstructure as shown in FIG. 3 permits resin readily to impregnate theinner layers from the outside. In this embodiment there is no need tosew a seam in inner reinforcing layer 53 and seam 66 in outerreinforcing layer 62 is sewn along the edge of the outer overlap asshown in FIG. 11 with a comparatively weak thread. This will hold theoverlap in position during the wet out process. This sewing thread ofseam 66 is designed to break under the influence of the inflationpressure to allow the overlap to slide.

Referring now to FIG. 12, a schematic illustration of a typical eversionof a cured in place pipe liner for rehabilitation of an existing conduit31 from a first manhole access 32 to a second manhole access 33. Animpregnated composite liner 36 of the type described in connection withliner 11 of FIG. 1 that has been wet out with resin is supplied in afolded configuration 37. Liner 36 is fed over rollers 38 to a down tube39 in a form of an elbow terminating at access to an underground conduit31. Liner 36 is fed through down tube 39, folded back and banded to theendpoint of down tube 39. An everting fluid, such as water in areservoir 41 is fed via a pump 42 to down tube 39 thereby turning liner36 inside out and into existing conduit 31. Resin impregnated into liner36 can be cured by any known means such as by application of heat,various forms of radiations, ultrasonics or other known energy means.After cured, liner 36 becomes a new pipe within existing conduit 31.

As can be readily seen, there is provided a convenient means ofincreasing the hoop strength and resistance to buckling of a flexiblecured in place liner while substantially decreasing the amount ofthermosetting resin utilized. Consequently, the cost to form the linerhaving strength greater than that possible without the reinforcement isobtained. By disposing high-strength low-elongation reinforcing fibersaround the inner surface and around the outer surface to provide asandwich construction that provides substantially increased hoopstrength is provided. This allows a significant advantage over the priorart suggestions of disposing various types of reinforcing layerssandwiched between resin absorbent layers or by disposing and/orwrapping various types of random chopped filaments either within orabout the resin absorbent layers.

It may be also desirable to include longitudinal reinforcing fibers tocontrol longitudinal stretch in either or both of the reinforcinglayers. These fibers are sewn into the fabric by the same threads thatsecure the circumferential high strength fibers. A longitudinalreinforcing fiber can be any high-strength low-elongation fiber, such asglass, polyester, polypropylene, nylon, carbon, Aramid and even steel.

It will thus be seen that the object set forth above, among those madeapparent from the preceding descriptions, are efficiently attained and,since certain changes may be made in carrying out the processes, in thedescribed products and in the construction set forth without departingfrom the spirit and scope of the invention, it is intended that allmatter contained in the above description and shown in the accompanyingdrawings will be interpreted as illustrative and not in a limitingsense.

It is also understood that the following claims are intended to coverall of the generic and specific features of the invention hereindescribed and all statements of the scope of the invention which, as amatter of language might be said to fall therebetween.

Particularly, it is to be understood that in the claims, ingredients orcompounds recited in the singular are intended to include compatiblemixtures of such ingredients, whenever the sense permits.

1. A composite tubular liner suitable for the trenchless rehabilitationof existing conduits, comprising: at least one layer of a resinabsorbent material joined at its edges in tubular form; at least onelayer of a plurality of bundles of high modulus fibers disposedcircumferentially on both the inner and outer surfaces of the at leastone layer of resin absorbent material; an impermeable layer disposedabout the outer layer of high modulus fibers; and the bundles of highmodulus fibers aligned circumferentially on both sides of the resinabsorbent layer with the ends of the bundles overlapping so that uponinstallation and expansion of the tubular composite, the ends of thehigh modulus fibers slide past each other to allow for expansion to thewall of the existing conduit before the resin is cured.
 2. The compositetubular liner of claim 1, wherein the resin absorbent material is aneedled felt.
 3. The composite tubular liner of claim 2, wherein theneedled felt is polyester.
 4. The composite tubular liner of claim 1,wherein the resin absorbent material is joined by one of a butt seam,flame bonding and adhesive.
 5. The composite liner of claim 1, whereinthe inner layer of high modulus fibers are disposed on and secured to aporous substrate.
 6. The composite liner of claim 5, wherein the poroussubstrate is a polyester netting.
 7. The composite liner of claim 5,wherein the porous substrate is a resin absorbent material.
 8. Thecomposite liner of claim 5, wherein the high modulus fibers on the innersurface of the resin absorbent material are joined to the substrate bylongitudinal stitching substantially perpendicular to the bundles offibers.
 9. The composite liner of claim 1, wherein the outer layer ofhigh modulus fibers are disposed on and secured to a porous substrate.10. The composite liner of claim 9, wherein the high modulus fibers arejoined to the porous substrate by longitudinal stitching substantiallyperpendicular to the bundles of fibers.
 11. The composite tubular linerof claim 1, wherein the high modulus fiber is selected from the groupconsisting of glass, polyester, polypropylene, nylon, carbon, Aramid(aromatic polyamide), steel and mixtures thereof.
 12. The compositetubular liner of claim 1, wherein the high modulus fiber is carbonfiber.
 13. The composite tubular liner of claim 12, wherein the carbonfibers are disposed in tows containing between about 30,000 to 100,000individual fibers of between about 200 to 750 feet per pound.
 14. Thecomposite tubular liner of claim 1, wherein the high modulus fiber isglass fiber.
 15. The composite tubular liner of claim 14, wherein theglass is a type E glass in bundles with strands having a continuouslength of about 100 to 1,000 feet per pound.
 16. The composite tubularliner of claim 1, wherein the at least one outer layer of high modulusfibers are joined by stitching substantially perpendicular to thesubstantially parallel bundles of fibers.
 17. The composite tubularliner of claim 1, wherein the high modulus fibers in at least one of thelayers of high modulus fibers are joined joined at their edges with thejoined edges folded back over the fibers to allow for expansion beforethe resin is cured.
 18. The composite tubular liner of claim 1, whereinthe high modulus fibers are disposed circumferentially around the resinabsorbent layer with the ends of the bundles overlapping to allow forexpansion before cure and provide for overlap of the bundles.
 19. Thecomposite tubular liner of claim 1, wherein the impermeable layerdisposed on the outer layer of high modulus fibers includes resinabsorbent material on the inner surface forming a bond with resin in theresin absorbent layer after cure.
 20. The composite tubular liner ofclaim 1, wherein at least one of the layers of reinforcing fibersincludes a high tensile strength fiber in the axial direction.